The snow biome (or maybe others to) dont end until i get striped biomes.

I have a 1.4.7 world were i tried new stuf in it. i copied the new snapshot an started the world again.
I was in a snow biome and searched for an other biome put i kept flying for like 5 minutes and the snow biome didnt end. until i got stripes of snow biome (see attachmend)